The present invention relates to a developer supplying device for supplying a developer to a developing device of an image forming apparatus such as a copying machine, a printer, a facsimile or the like in which a powder developer is used.
An image forming apparatus is provided with a developer container removable therefrom. The developer drops from the container to the storing section thereof. Thereafter, the developer is supplied to a developing device through a toner transporting means.
However, according to the known art, the image forming apparatus requires a space for mounting the developer supplying container in addition to the storing section. Therefore, the image forming apparatus is large-sized. Furthermore, after the developer is supplied from the developer supplying container to the storing section, the space for accommodating the developer supplying container is substantially unnecessary.
Another type of developer supplying container has been provided in order to reduce the space for mounting the developer supplying container. With such container, a spiral groove is formed on the inner peripheral surface of a cylindrical member having an opening on one end thereof. The cylindrical member is rotated so that a developer is transported toward one end of the container along the spiral groove. The developer is supplied to the developing device directly through the opening. This construction eliminates the need for the provision of a developer storing section. Thus, an image forming apparatus is small-sized.
However, according to the above-described developer supplying container, the amount of a developer supplied from the opening thereof to the developing device greatly varies depending on the amount of the developer accommodated therein. As apparent from the graph of FIG. 6 in which the horizontal axis shows the number of rotations (developer supply period) of the developer supplying container and the vertical axis shows the supply amount of the developer per rotation of the developer supplying container, the amount of the developer which drops from the opening thereof gradually increases with the increase of rotations thereof and decreases from the peak value of rotations thereof. That is, the amount supplied by the developer supplying container per rotation always changes. Therefore, it is very difficult to control the amount and density of the developer in the developing device.
U.S. Pat. No. 4,641,945 discloses a developer supplying device for supplying a developer by rotating a cylindrical member having a spiral groove formed on the inner peripheral surface thereof.
The developer supplying device comprises a developer supplying container, a holding section for holding the developer supplying container, a driving section for rotating the developer supplying container mounted on the holding section, and a transporting section for transporting a developer supplied from the developer supplying container to the developing section of an image forming apparatus.
The developer supplying container comprises the spiral groove extending axially along the inner peripheral surface of the cylindrical member, a gear formed along the peripheral surface thereof, and a developer supplying opening positioned in the front section thereof. The holding section of the developer supplying container comprises a developer receiving opening, a cap into which the front section of the developer supplying container can be inserted, and a supporting frame for supporting the rear section of the developer supplying container and urging the developer supplying container toward the cap. The driving section is positioned alongside the holding section and includes a driving gear which engages a peripheral gear of the developer supplying container mounted on the holding section. The transporting section communicates with the developer receiving opening of the holding section and has a developer transporting means.
In the developer supplying device, the developer supplying container is accommodated in the holding section with the front section thereof having the developer supplying opening inserted into the cap and the rear section thereof supported by the supporting frame. In this condition, the supporting frame urges the developer supplying container toward the cap. The peripheral gear engages the driving gear of the driving section.
The developer supplying container is rotated by the rotation of the driving gear. As a result, the developer accommodated therein is fed toward the forward section of the cylindrical member along the spiral groove. Thus, the developer is supplied from the developer supplying opening to the transporting section through the developer receiving opening. Thereafter, the developer which has been transported to the transporting section is transported to the developing section.
According to the above developer supplying device, gear provided along the peripheral surface of the developer supplying container engages the driving gear positioned alongside the holding section. That is, the developer supplying container is rotated by a tangential force applied to the peripheral surface of the developer container. However, the tangential force is not uniformly applied to the periphery of the developer supplying container.
Accordingly, the rotational axis of the developer supplying container mounted in the holding section is displaced, so that the developer supplying container is shaken in the holding section. As a result, the contact position and the frictional force between the cylindrical developer supplying container and the holding section vary, so that a load applied to the driving gear varies to a great extent. In addition, the opening of the developer supplying container does not align with the developer introducing opening of the holding section communicating with the opening of the developer supplying container. Consequently, the developer is spilt from the gap between the two openings, thus polluting the periphery of the developer supplying container. Further, the developer spilt from the gap penetrates into the gap between the developer supplying container and the holding section. As a result, the frictional force between the developer supplying container and the holding section becomes great, and a load applied to the driving gear increases.
Furthermore, the above-described developer supplying device has the following problem. It is troublesome to mount the developer supplying container in the holding section. That is, it is necessary to move the supporting frame backward to provide a sufficient space between the cap and the rear wall of the supporting frame.
Additionally, it is necessary for the holding section to provide two members, the cap and the supporting frame, and also provide a spring for urging the supporting frame toward the cap. Thus, the number of parts to be assembled increases and it is troublesome to assemble the parts.